You bring up two legitimate reasons for concern regarding his prime and being a repeat offender.
If after a thorough vetting it was determined he had changed and overcome his addiction the repeat offender part should no longer be an issue.
And after a thorough physical assessment it’s determined that he still has it physically then the past his prime concern should no longer be an issue either.
Both concerns require thorough vetting.
But if he passes both of those tests, building conservatively and preserving space for Spruce and the other young receivers are not legitimate reasons to not sign him IMO.
Spruce and the other young guys were late round draftees and UDFAs for good reasons. Worrying about their status on the pecking order is not a good reason to avoid a supremely talented receiver.